Field of the Invention
The present invention relates to an image forming apparatus including an openable door.
Description of the Related Art
Hitherto, an image forming apparatus such as a printer is provided with an openable door on a side surface of an apparatus body such that the door can be opened for the purpose of removing a jammed sheet or of maintaining the apparatus. In such an image forming apparatus, the door is generally configured such that the door moves to an open position by its own weight when a user removes his/her hands from the door when opening the door so that the door does not stop at a mid-position between a closed position and an open position.
By the way, when the door moves to the open position as the user removes his/her hands from the door, a large impact force is generated on the door and the image forming apparatus body. Then, conventionally, an oil damper is provided in an opening/closing mechanism of a cover of the image forming apparatus as an impact relieving portion for relieving such impact by reducing a moving speed of the door in an opening direction, as disclosed in Japanese Patent Application Laid-open Nos. 2006-83551 and 2007-279274. Still further, an image forming apparatus can be provided with a spring to bias the door in a closing direction to restrict the moving speed of the door in the opening direction, as disclosed in Japanese Patent Application Laid-open Nos. 2003-241466 and 2009-134227, for example.
Here, in relieving the impact generated in opening the door by using the impact relieving portion, it is necessary to set a braking force of the impact relieving portion to reduce the moving speed of the door in the opening direction while assuming a maximum value of the impact force, or operation force generated in opening the door. Here, if the impact relieving portion is used, it is necessary to assess a maximum value of the operation force applied by the user in opening the door and others, and to balance various aspects such as compatibility of the impact relieving portion and the operation force of the user, cost performance of the configuration of the impact relieving portion, and others.
However, the image forming apparatus is restricted variously due to its entire configuration in reality, and there are various problems in setting the configuration and the braking force of the impact relieving portion. If a rotary damper is used as the impact relieving portion, for example, it is necessary to configure the rotary damper such that a force of opening the door generated by the weight of the door itself exceeds a restricting force of the rotary damper within a range in which the rotary damper effectively functions within an opening/closing operational area of the door.
In this case, a force generated when the user vigorously opens the door wholly becomes an impact force. That is, it is important to assume how much force the user applies to the door in setting a rotational load of the rotary damper. If the force applied to the door is underestimated here, and if a force greater than the estimation is applied to the door, not only can damage occur to the door itself or components related to the door, but also to the body of the image forming apparatus and a frame composing the frame body in particular. In contrast, if the force applied to the door is overestimated, it may become difficult to move the door to the open position by the weight of the door itself, and hence operability thereof is reduced.
Meanwhile, in the case of a configuration using a spring as the impact relieving portion and of relieving the impact in opening the door by applying resistance in the opening direction of the door, the same problems as those which arise when the rotary damper is used are assumed to occur in setting a strength of a spring force. Still further, because the force of the spring is applied in a direction of closing the door when the spring is used, and the spring bias force is added to the operation force of the user in closing the door, speed of the door is accelerated as the door approaches the closed position. Therefore, it is also necessary to consider the relief of the impact in closing the door.